Even-even nucleus
= Even-even nucleus
An <atomic nucleus> with even <proton> number $Z$ and even <neutron> number $N$. The simple <nuclear pairing> picture couples the constituent pairs to zero <angular momentum>. The collective examples below concern a $0^+$ <ground state>, where the superscript denotes positive <parity>, and its associated low-lying excitations; even $A=Z+N$ alone would also allow odd $Z$ and odd $N$.